Osrhoena

Osrhoena was a Roman province which existed from 244 to 637 AD, with Edessa serving as its capital. The Roman Empire absorbed the kingdom of Osroene in 244, and it became a frontier province against Sassanid Persia. The Persians virtually conquered the Roman east during the 250s, but King Odaenathus of Palmyra drove out the Persians in 261. The province was taken and retaken several times, and Legio III Parthica was stationed at Resaena. It continued to be a Roman province until its conquest by the Rashidun Caliphate in 637.